Java Instance return model note!_returnmodeltype entities-优快云博客

本文讨论了在Java类中使用静态方法`getInstance()`可能导致的问题，即两个不同的对象实例化导致的失败返回。通过引入`instance`变量并使用`synchronized`关键字，解决了对象实例化顺序问题，确保了代码的正确执行。

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1. We have a class and define a static method of getInstance()

public class GenDarwinGlobal extends GenDarwinGlobalHelper
{
    /**
     * Script Name   : <b>GenDarwinGlobal</b>
     * Generated     : <b>Mar 31, 2011 1:16:48 AM</b>
     * Description   : Functional Test Script
     * Original Host : WinNT Version 5.2  Build 3790 (S)
     *
     * @since  2011/03/31
     * @author dwei
     */
    public void testMain(Object[] args)
    {
        // TODO Insert code here
    }
    public  static GenDarwinGlobal getInstance()
    {
        return new GenDarwinGlobal();
    }
}

2. Compare these code line, the getInstance sequence will get failed return because it has two new instance belong to different object.

//        FucLib.GenevaFuc.GenDarwinGlobal.getInstance().openBuyTransaction();
    //    FucLib.GenevaFuc.GenDarwinGlobal.getInstance().ClickQuery();


        FucLib.GenevaFuc.GenDarwinGlobal oGD =  new FucLib.GenevaFuc.GenDarwinGlobal();
        oGD.openBuyTransaction();
        oGD.ClickQuery();

3. Also we can using this method to resolve this problem in the instance code .

private static GenDarwinGlobal instance = null;
public static synchronized GenDarwinGlobal getInstance()
{
   if( instance == null)
   {
    instance = new GenDarwinGlobal();
   }
    return instance;
}